Figure 1.

Characterization of the metal nanoparticles with different sizes and porosities. a) Transmission electron microscopy (TEM) images of three different sizes of metal nanoparticles with typical structures (silver nanocube with a solid inner). The edge lengths of them were about 50, 100, and 150 nm, namely NP50‐0, NP100‐0, and NP150‐0, respectively. b) TEM images of metal nanoparticles with the increasing porosities, which were synthesized by using the as‐prepared solid nanocubes as sacrificial templates, and then reacting with increasing amounts of HAuCl₄ solution via the galvanic replacement reaction, as schematic illustrating in (c). The increasing porosity of the product was defined from 0 (no porosity) to 4 (the highest) status in each size level. d–g) Optical characterization of the products by UV–vis spectroscopy. The inserted pictures were the photograph of the as‐synthesized metal nanoparticles at various sizes: e) 50 nm; f) 100 nm; g) 150 nm and porosity (increasing from left to right). h) The size distribution and i) zeta potential of dispersed nanoparticles in aqueous were analyzed by dynamic light scattering and phase analysis light scattering, respectively. The inserted pictures showed the average size and the average zeta potential of the series of the products.